Crust: In a small
bowl, combine crumbs and butter. Mix well. Press into bottom of and 8 inch spring form pan.
In a large mixing bowl, using an electric mixer set on medium speed, beat cream cheese and sugar for 2 minutes. Beat in sour cream, flour and vanilla, add the eggs 1 at time beating well after each addition.
Transfer 1 ½ cups of batter to a small bowl. Stir in chocolate. Spread half of vanilla batter over crust. Top with half
of chocolate batter. Layer on remaining vanilla batter then top with remaining chocolate batter. Using a knife, gently swirl batters together. Place pan in a shallow roasting pan. Add enough
boiling water to come half way up sides of the
spring form pan. Bake until just set - about 1 hour 15 minutes.
Place pan on a wire rack and cool to room temperature. Cover and chill for 4 hours.